Corrosion inhibitor



Patented Dec. 24, 1940 UNITED STATES 2,225,866 CORROSION INHIBITOR JohnB. Holtzclaw, Roselle, and Anton Harmsen and Henry H. Cooke, Elizabeth,N. 1., assignors to Stanco, Inc.

No Drawing. Application December 31, 1938, Serial N0. 248,866

6 Claims.

This invention relates to an improvementin heat transfer media for usein automobile radiators, heating systems-where the transfer of heatdepends upon the circulation of aqueous fluids and any other mechanicaldevices where aqueous solutions come in contact with metals.

More particularly, this invention pertains to heat transfer mediacontaining freezing point depressants, such as alcohols, glycols andglycerine. Water alone is very corrosive to iron, steel and the alloysof base metals. The corrosive action of water upon metals is greatlyenhanced by the addition thereto of freezing point depressants, such asalcohol or glycol, which is presumed to be due to the oxidation productsof the freezing point depressant formed in the aqueous solution. Thecooling system of an automobile consists of a water jacket around thecylinders, a radiator for exposing a large surface to the cooling actionof the air, a pump for circulating the cooling fluid and necessaryflexible couplings between the parts. The water'jacket is generally madeof iron and provides the source of the most troublesome corrosionproblem due to the fact that the iron rust formed therein circulateswith the cooling fluid lodging in and clogging up the small passagewaysin the radiator. An automobile radiator is ordinarily made of brasswhich is also subject to corrosion by aqueous solutions, but theproducts of corrosion of brass are not so voluminousas iron rust andtherefore do not obstruct the passageways of the radiator to so great anextent. The corrosion problem in radiators is one of preventing leaks.

The radiator is made of very thin metal which would soon be eaten thruif unabated corrosion were permitted. The major part of the corrosion inautomobile cooling systems occurs in the water jacket and radiator, andafiords the most serious obstacle to emcient control of the temperaturein the combustion chamber.

Various attempts have been made using corrosion inhibitors, such assodium nitrite or sulionic acid salts, to control corrosion. The resultsobtained by these attempts have not been entirely satisfactory owing tothe varied composition of the component parts of the mechanism.

An object of this invention is to provide a composition which willfurnish a means for eliminating substantially all corrosion from systemsusing aqueous fluids as heat transfer media. In addition, as will beevident from the description which follows, this new compositionpossesses further advantages over previously employed materials, and itis a further object of this invention to utilize these advantages to thefullest extent as they may appear.

Oil-soluble salts of sulfonic acid have been used to inhibit thecorrosion of metals.

A typical antifreeze solution in which an oil-soluble sulfonate providesthe protection against corrosion is:

It has also been quite common to use sodium tetraborate or borax as acorrosion inhibitor. A typical anti-freeze mixture employing borax asthe corrosion inhibitor would be:

Formula B Percent by volume Methanol 53.25 91% Isopropanol 44.65 Mineraloil distillate 1.50 Water 0.50 Water-soluble dye (1% solution) 0.10

Per cent wt./vol. Borax 0.2

It has now been found that ii a combination of borax and oil-solublesulfonates are used in aqueous solutions as the corrosion inhibitor, thecombination is much more effective in preventing metal corrosion thaneither one used separately.

A typical anti-freeze formula, employing both borax and oil-solublesulfonates, is:

Formula 0 Percent by volume Me hanol 53.55 91% Isopropanol 44.57 Mineraloil distillate 1.50 Water 0.50 Water-soluble dye (1% solution) 0.10

Per cent wt./vol. Sodium rosinate or equivalent .05 Borax 0.1Oil-soluble sulfonates .08

The marked superiority of Formula C over either Formulae A or B will bemade readily apparent by a comparison of the corrosion data tabulated inTable 1.

The further surprising discovery has been made that if suflicientalkali, either in the form of sodium hydroxide, sodium carbonate orother alkali, is added to a 40% solution of Formula C in tap water toraise the pH of the solution to 11 or 12, the anti-corrosion action ofborax and oilsoluble sulfonates is further greatly enhanced. A typicalexample, employing this principle, is:

Formula D Per cent by volume Methanol 63.90 91% isoprop 31.40 Mineraloil distillate 2.00 Water 2.40 Water-soluble dye (1% solution) 0.10

Per cent wt./vol. Borax 0.2 Sodium rosinate or equivalent 0.1 Sodiumhydroxide 0.2 Oil-soluble sulfonates 0.3

The pH value-of a 40% solution in tap water of the above disclosedexamples would be as follows:

Formula A 6.5 to 7 Formula B 9.5 to 10 Formula C 9.5' to 10 Formula D 11to 12 A certain latitude is permissible in Formulae c and D as to theamounts of borax, sodium rosinate, oil-soluble sulfonates or sodiumhydroxide added. The range within which these substances may be used is:

rosive efiect on metals of the above described formulae, strips ofsteel, cast iron, aluminum, brass and solder of uniform size wereobtained. 40% solutions of the previously described formulae were madeup and placed on a steam bath where they could be maintained at auniform temperature of about F. The metallic strips, after beingweighed, were suspended from glass rods and immersed in the hot solutionwhere they remained for one month. After one month the strips wereremoved, washed, dried and weighed. This test is equivalent toapproximately one seasons use of the solution under ordinary conditions.The results of the test appear in Table 1 The above table shows thatFormula C is distinctly better than Formula A except for its action uponaluminum where it is, however, equally as good. It is also shown thatFormula C is an improvement over Formula B in its action upon all of themetals. The most surprising results, however, were obtained in the useof Formula D which was found to have no corrosive action upon eithersteel, cast iron or aluminum. It is noted that in Formula D the solderstrip sustained a greater loss than the solder strip used in testingFormula C but the corrosion exerted upon solder by Formula D is stillconsiderably less than the corrosion of solder exhibited by Formulae Aand B. As a general rule, solder is badly corroded by alkaline solutionsbut is impervious to weak acid solutions. However, cast iron forms thepredominant part of either an automobile cooling system or other aqueousheat exchange equipment and consequently must be the metal given primeconsideration when experimenting with corrosion inhibitors for use inthis connection. A compromise must therefore be made due to the varietyof metals and alloys in use to obtain the inhibitor offeringjhe greatestprotection to the chief metal at the least possible sacrifice ofprotection to the other metals. Formula D then is such a formulaoffering, as it does, complete protection to steel, cast iron andaluminum, and substantially complete protection to copper alloys andsolder.

In systems utilizing water, either in the liquid or vapor phase, wherefreezing point depressants are either unnecessary or undesirable andwhere cast iron or steel is the prevailing metal, corrosion at timesreaches prohibitive proportions. The corrosion inhibitor of thisinvention is as suitable for preventing corrosion under these conditionsas it is where freezing point depressants are present. A typical formulafor use in the absence of freezing point depressants would be:

Per cent Borax 25.0 Sodium rosinate 12.5 Sodium hydroxide 25,0Oil-soluble sulfonates 37.5

When added to water in amounts varying between 1.25 grams to 6.25 gramsper gallon, according to the hardness of the water, this compositionwill protect any iron, steel or alloys coming in contact with thetreated water against virtually all corrosion.

While there are above disclosed but a limited number of embodiments ofthis invention, it is possible to produce still other embodimentswithout departing from the inventive concepts herein disclosed and it istherefore desired that only such limitations be imposed on the appendedclaims as are stated therein.

We claim:

1. An anti-freeze fluid comprising an alcohol, mineral oil distillate 1to 3%, oil-soluble sulfonates .08-.3%, water 1.0-5.0%, borax .1-.5%,soap .05-.2%, water-soluble dye .001% and suflicient alkali to give a pHof at least 9.5 to a 40% solution of the anti-freeze in water.

2. An anti-freeze fluid consisting of an alcohol 95.30%, mineral oildistillate 2.00%, water 2.40%, oil-soluble sulfonates 0.3%, sodiumrosinate 0.1%, borax 0.2%, water-soluble dye .001% and sufiicient alkalito give a pH of at least 9.5 to a 40% solution of the anti-freeze inwater.

3. An anti-freeze fluid consisting of methanol 63.90%, isopropanol31.40%, mineral oil distillate 2%, oil-soluble sulfonates 0.3%, water2.4%, borax 0.2%, sodium rosinate .1%, water-soluble dye .001% andsodium hydroxide in an amount suflicient to adjust a 40% solution of theantifreeze in water to a pH of 11.

4. An anti-freeze fluid consisting of ethyl alcohol 95.30%, mineral oildistillate 2.00%, water 2.40%, oil-soluble sultonates 0.3%, sodiumrosinnate 0.1%, borax 0.2%, water-soluble dye .001% and sufficientalkali to give a. pH of at least 9.5 to a. 40% solution of theanti-freeze in water.

5. An anti-freeze fluid consisting of methyl alcohol 95.30%, mineral oildistillate 2.00%, water 2.40%, oil-soluble sulfonates 0.3%, sodiumrosinate 0.1%, borax 0.2%, water-soluble dye .001% and sufficient alkalito give a pH of at least 9.5 to a. 40% solution of the anti-freeze inwater.

I 6. A corrosion inhibitor for use in aqueous heat exchange mediacomprising borax 23-34%, soap 11.5-13%, oil-soluble sulfomtes 18.520%and alkali 3446.570.

JOHN B. HOLTZCLAW. ANTON HARMSEN. HENRY H. COOKE.

